Patch from Debian: "use system leptonica", see
https://sources.debian.org/patches/k2pdfopt/2.55%2Bds-2/0005-willuslib-use-system-leptonica.patch/

Index: willuslib/wleptonica.c
--- willuslib/wleptonica.c.orig
+++ willuslib/wleptonica.c
@@ -23,7 +23,7 @@
 #include "willus.h"
 
 #ifdef HAVE_LEPTONICA_LIB
-#include <leptonica.h>
+#include <leptonica/allheaders.h>
 
 static void wlept_pix_from_bmp(PIX **pixptr,WILLUSBITMAP *bmp);
 static void wlept_bmp_from_pix(WILLUSBITMAP *bmp,PIX *pix);
@@ -135,7 +135,7 @@ pixWrite("pixb.png",pixb,IFF_PNG);
     dew1=dewarpCreate(pixb,1);
     pixDestroy(&pixb);
     dewarpaInsertDewarp(dewa,dew1);
-    dewarpBuildPageModel_ex(dew1,debug,fit_order);
+    dewarpBuildPageModel(dew1,debug);
     if (bmp1!=NULL)
         {
         PIX *pix2,*pix2d;
